Fuel injection pumps for internal combustion engines



FUEL INJECTION PUMPS FOR INTERNAL COMBUSTION ENGINES Filed March 23, 1959 DBDDDDD INVENTORS HERBERT H. B Mme-r1 KENNETH W. CcuesE.

ATTORNEYS signors to D. Napier & Son Limited, London, England, 'a British company Filed Mar. 23, 1959, Ser. No. 801,034

Claims priority, application Great Britain Feb. 28, 1956 1 Claim. (Cl. 103-154) This invention relates to fuel injection pumps for internal combustion engines, of the kind comprising a barrel in which slides aplunger, the fuel being forced by the plunger out of the barrel at high pressure through a delivery valve and into a fuel delivery pipe or pipes leading to .one or more injectors which spray the fuel into a cylinder of the engine.

For certain types of engine there is a demand for what may be termed an ultrahigh pressure pump, i.e. a fuel injection pump which will deliver fuel at a considerably higher. pressure than is obtainable with fuel injection pumps of conventional design. One factor which is essential for an ultra high pressure fuel pump is that the plunger's'hall bean extremely close and accurate fit in the barrel, to avoid leakage of fuel between the plunger and the barrel duringthe pressure stroke of the pump. To providesuch accuracy it is necessary that the interior of the barrel in which the plunger slides shall be finished by means of a lapping operation using a hone, and that the hone shall be capable of being passed right through the barrel; It is not practicable to obtain the desired accuracy of finish if the hone has to be stopped in the barrel and withdrawn in the opposite direction.

it is also necessary that there shall be a minimum of radial distortion of the barrel due to clamping forces applied to the barrel. Another problem which is encountered in an ultra high pressure pump is to seal the joints in the pump which are subjected to the very high pressure. Indeed, failure of a high pressure seal must .be expected from time to time, and it is generally important for operation of the engine, particularly a multi-cylinder engine, that such failure, shallnot go undetected, since this may lead to over fueling of the other cylinders either by automatic or manual control in an attempt to maintain the power output.

It is an object of this invention to provide a fuel injection pump suitable for ultra high pressure operation which meets the above-mentioned requirements.

This and other objects of the invention will be explained more fully in connection with a specific embodiment which will be described with reference to the accompanying drawing, which is a sectional side elevation of the upper part of one form of ultra high pressure pump embodying the invention.

The fuel pump of the present invention embodies, in combination, a number of different features which all contribute essentially to fulfilling these objects. Although certain of these features are known in themselves, they have not hitherto been employed in this particular combination, and it is only by this novel combination and corelation of these several features that the desired objects of the invention are achieved.

One of these features is that the barrel and delivery valve housing of the pump are made as a one-piece unit. Although it is known to make the delivery valve housing and the barrel as a one-piece unit, in the conventional construction of a fuel pump the barrel is made as a Owing to .the extremely accurate fit of the plunger in the barrel States [Patent separate part from the delivery valve housing, the mat ing faces of these parts being accurately finished and the two parts being held tightly together with a strong clamp In the usual con:

ing force to prevent leakage of fuel. ventional construction, the pump barrel has anexternal shoulder which engages a seating formed in a recess in the;

pump body, which is an aluminium or aluminium alloy casting, and the delivery valve housing either screws into the recess in the pump body or has an external shoulder engaged by a ring nut which screws into this recess. The

force with which the delivery valve housing and the pump barrel are clamped together is determinedby the force applied by the ring nut, the reaction of this force being transmitted through the pump body. The pump body 'not only has to sustain this constant clamping force, but

also the reaction of the pump force app-lied by the plunger. Such conventional designs are not satisfactory when pumping pressures substantially higher than conventional pumping pressures are required, since at ultra high' pressures both the clamping force and the reaction of the pumping force are very large and may be so high as to distort the pump body. Moreover, if the matingfaces of the barrel and the separate delivery valve housing are not extremely accurate, or these parts are not clamped sufficiently tightly together, leakage-may occur between thesefaces, and since these facesare clamped together within the'pump body the leaking fuelwill not be visibleto the operator.

By providing a one-piece barrel and deliveryvalve housing unit this problem is overcome. leakage between the pump barrel and the delivery valve housingis completely eliminated, and, moreover, it is no diameter-upper part of said bore containing the delivery valve of the pump and the delivery valve spring. Since the lower part of the-bore in which the plunger slides hasthe smallest diameter of any part of the bore, that is to say; there 'is no smaller diameter valve seating or similar obstruction, a lapping hone can be passed right through the bore during the finishing operatiomwhereby the bore can be given the extremely accurate finish necessary for ultra high pressure operation.

A further feature of the invention is that there is a recess in the pump body provided with a seating, an external seating shoulder on said one-piece barrel and delivery valve housing unit engaging said seating in the body, an external clamping shoulder on the said unit spaced above said seating shoulder, and a clamping nut screwed into said recess in the body, a crush washer being interposed between the clamping nut and the clamping shoulder on the unit. Said clamping nut applies a compressive clamping force to the unit between said seating shoulder and said clamping shoulder in a direction substantially parallel with the axis of the bore. By applying the clamping force in this direction, radial distortion of the barrel due to the clamping force is virtually eliminated. The crush washer ensures that the force applied by the clamping nut is distributed uniformly around the circumference of the barrel. The crush washer is necessary because it is not always practicable, using conventional production techniques, to ensure that the plane of said seating in the recess in the body is exactly perpendicu- Patented Nov. 29, 1960 7 Thus, the risk of lar to the axis of the screwthread in this recess which receives the clamping nut.

Referring now to the accompanying drawing, in which only those parts are shown which are necessary for a proper understanding of the invention, there is shown a fuel pump suitable for delivering fuel at ultrahigh pressures. The pump comprises a cast pump body made of aluminium or aluminium alloy, having in its upper portion a recess 42 accommodating a one'piece pump barrel and delivery valve housing unit 11. In the barrel there reciprocates a pump plunger 12. The delivery valve housing portion '13 of said unit accommodates a delivery valve 14 which is urged towards a seating 48 in said unit by a compression spring 15. Screwed on to the upper end of housing portion 13 is a T-connec-tor 16 to which can be attached fuel delivery pipes (not shown) leading to two fuel injectors. Squeezed between the upper end of housing portion 13 and the interior of T-connector 16 is a high pressure sealing washer 43.

Said one-piece barrel and delivery valve housing unit 11 is provided with an external seating shoulder 17 which seats upon a corresponding seating 18 formed in the base of recess 42 in pump body 10.

Unit 11 is also provided with an external clamping shoulder 19 upon which lies a crush washer 44 and upon which in turn presses an internal shoulder 20 formed in a ring nut 21 which surrounds housing portion 13 and which screws into a screwthread 49 in said recess 42. In view of the substantial longitudinal distance between shoulders 17 and 19, the force produced by ring nut 21 is practically parallel with the axis of the pump barrel. The crush washer 44 ensures that said force is distributed uniformly around clamping shoulder 19, even though in some instances the axis of said screwthread in the recess 42 may not be exactly perpendicular with the plane of seating 18 at the bottom of the recess.

Since said barrel and delivery valve housing are made in one piece no clamping force has to be provided to prevent leakage between these parts, as would be necessary if they were formed separately in the conventional manner. Consequently, ring nut 21 does not have to transmit any such clamping force to pump body 10, the only force which these parts 21 and 10 have to resist being the reaction of the pumping force. 7 Moreover, there is no high pressure seal at a lower level than sealing washer 43, and since the lower end 45 of T-connector 16 terminates substantially above the top surface 46 of pump body 10 there is no risk of fuel which may leak past the seal 43 in the event of partial failure of this seal entering the interior of pump body 10 without first being visible on the exposed outer surface of delivery valve housing portion 13.

It is sometimes desirable to flush the pump and fuel delivery pipes to remove air bubbles. This can be done by loosening the connections between the fuel delivery pipes and the injectors, raising delivery valve 14 from its seating 48 and pumping fuel through the pump and delivery pipes at relatively low pressure. To facilitate raising delivery valve '14, T-connector 16 is provided with a removable plug 33 screwed into a hole directly opposite delivery valve 14. After removing plug 33 a threaded wire or rod can be inserted through said hole to engage a correspondingly-threaded hole 47 in the top of delivery valve 14. The wire or rod is then pulled upwardly to raise delivery valve 14 off seating 48 against the action of spring 15. Suitable packing is then inserted into the plug hole around the rod or wire and flushing fuel is passed through the pump and delivery pipes at low pressure.

This application is a continuation-in-part of application Serial No. 635,658, filed January 23, 1957, and now abandoned.

What we claim as our invention and desire to secure by Letters Patent is:

A fuel injection pump for an internal combustion engine comprising a pump body having a recess therein, a screwthread in said recess, a one-piece barrel and delivery valve housing unit mounted in said recess with a portion projecting out of said recess, externally of said body, said unit having a stepped bore extending throughout its length, a plunger slidable in a lower part of said stepped here which part has the smallest diameter of any part of said bore, a delivery valve contained in an upper part of said bore which is of larger diameter than said lower part, a delivery valve spring contained in said upper part of said bore, seating in said recess in said pump body, an external seating shoulder on said unit engaging said seating in said body, an external clamping shoulder on said unit spaced above said seating shoulder, a clamping nut screwed into said screwthread in said recess, a crush washer interposed between said clamping nut and said clamping shoulder, said clamping nut applying a compressive force to said unit between said seating shoulder and said clamping shoulder substantially parallel with said bore, a fuel delivery pipe connector screwed on to said projecting portion of said unit externally of said body, and a sealing washer compressed between said unit and said fuel delivery pipe connector.

References Cited in the file of this patent UNITED STATES PATENTS 2,101,221 LOrange Dec. 7, 1937 2,126,985 Buckwalter Aug. 16, 1938 2,420,164 Brewser May 6, 1947 2,501,074 Meitzler Mar. 21, 1950 

